The present invention relates to cameras, and more particularly to a camera having improved film-transport actuation.
To advance film in a camera the user must operate an actuating element which causes the desired film advancement. Many proposals have been made in this respect. For example, it is known to provide knobs which are turned or slides which must be pushed or pulled. Other proposals include levers which are pivoted to effect rapid film transportation and, especially in the case of the larger roll film cameras, cranks which are turned. Still further prior-art proposals include rods or complete housing parts which are displaced with reference to the camera housing to transport the film, or rings which surround the lens and must be turned to effect film transportation. According to a proposal for a camera which uses film packs containing a number of film sheets, a tag of the respective film sheet extends from the camera and must be pulled to effect film-sheet transportation.
The particular structures of these prior proposals differ widely from one another. However, all of these proposals have one common denominator: the movement which must be performed to effect film transportation is always in a direction normal to, or circumferentially of, the optical axis of the camera lens.
In many instances this is not objectionable because the force required to effect such movement (and hence to transport the film) is often quite small. However, in some types of camera this force is much higher. For example, in the so-called instant-picture cameras the film sheets are relatively large and require a higher-than-usual force to transport them. More importantly, during the transportation of these film sheets a paste-like developer must be uniformly spread over the entire picture area of the film sheet; therefore, the transportation force must be sufficiently high to effect such spreading which usually occurs as the film sheet is moved through the nip between two spreading rollers.
In the prior-art cameras such higher forces are difficult for a user to produce, because a force which must act normal to or circumferentially of the optical axis is not easy to generate. Moreover, in the prior-art proposals the user must change his grip on the camera when he has completed an exposure and now operates the arrangement (button, lever, slide, and the like) which activates the film transport mechanism.
Cameras for large-format film, and instant-picture cameras, seek to overcome the force-application problem by either providing the earlier-mentioned pull-out tags or providing a mechanical (e.g. cranks, slides) or motorized drive for the film-transporting mechanisms. They still require, however, that the user change his grip on the camera in order to actuate this mechanism.